Antistatic and adherent compositions based on polyamide

Abstract

The present invention relates to antistatic and adherent compositions based on polyamide, which can be employed especially for the manufacture of composite materials and articles, such as multilayer pipes and/or conduits for conveying and/or storing hydrocarbons. The compositions contain carbon black and are employed for the production of pipes, containers and drums including: an inner layer in contact with the hydrocarbons, based on the said antistatic and adherent composition, a middle layer made of fluoropolymer, preferably of polyvinylidene fluoride, and an outer layer of polyamide, these layers being bonded to each other respectively by layers of adhesive binder. The invention also relates to a process for preparing these items.

What is claimed is: 
     
       1. An antistatic and adherent composition comprising polyamide, characterized in that the composition further comprises from 4.5% to 8% by weight of carbon black wherein the composition is simultaneously antistatic and adherent to at least one adhesive binder for fluoropolymers. 
     
     
       2. The composition of claim 1, characterized in that the composition is simultaneously antistatic and adherent to at least one adhesive binder for polyvinylidene fluoride. 
     
     
       3. The composition of claim 1, further characterized in that it comprises at least one polyamide selected from the group consisting of PA-12, PA-11 and PA-12,12. 
     
     
       4. The composition of claim 1 further comprising a plasticizer. 
     
     
       5. The composition of claim 1 comprising PA-12 with an inherent viscosity of approximately 1.45 in m-cresol, characterized in that the carbon black has a specific surface area of 1250 m 2  /g and a pore volume of 400 ml of dibutyl phthalate per 100 g of carbon black. 
     
     
       6. The composition of claim 5 comprising from 5.5% to 6.5% by weight of carbon black. 
     
     
       7. A process for the preparation of an antistatic and adherent composition comprising polyamide, characterized in that the composition further comprises 4.5% to 8% by weight of carbon black to be simultaneously antistatic and adherent to an adhesive binder for fluoropolymers, said process occurring in two stages, characterized in that in the first stage, a first composition is prepared by adding carbon black to a polyamide in a sufficient quantity such that the resistivity of the first composition is substantially identical to plateau region resistivity; and   in the second stage, diluting the first composition, the precise carbon black content thereof having been measured beforehand, with a polyamide substantially free of carbon black.   
     
     
       8. A composite material comprising at least these successive layers: the composition of claim 1,   an adhesive binder, and   a fluoropolymer.   
     
     
       9. The composite material of claim 8 wherein the fluoropolymer comprises polyvinylidene fluoride. 
     
     
       10. An article of manufacture selected from the group consisting of multilayer pipes, containers and drums for conveying hydrocarbons, characterized in that the article comprises: an inner layer in contact with the hydrocarbons, comprising the composition of claim 1,   a middle layer comprising a fluoropolymer, and   an outer layer comprising a polyamide, wherein the layers are bonded to each other by layers of an adhesive binder.     
     
     
       11. The article of manufacture of claim 10 wherein the middle layer comprises polyvinylidene fluoride. 
     
     
       12. The article of manufacture of claim 10 wherein the outer layer comprises at least one polyamide selected from the group consisting of PA-11, PA-12 and PA-12,12. 
     
     
       13. The article of manufacture of claim 12 wherein the outer layer comprises PA-12. 
     
     
       14. The article of manufacture of claim 10 wherein the inner layer comprises at least one polyamide selected from the group consisting of PA-11, PA-12 and PA-12,12. 
     
     
       15. The article of manufacture of claim 14 wherein the inner layer comprises PA-12. 
     
     
       16. The article of manufacture of claim 10 wherein the adhesive binder comprises at least one material selected from the group consisting of polyvinylidene fluoride homopolymer, a copolymer of the acrylic-imide type comprising acid and anhydride functional groups, and a methyl methacrylate-butadiene-styrene (MBS) impact modifier of the core-shell type. 
     
     
       17. A process for forming the composite material of claim 8 whereby the composite material is formed by at least one method selected from the group consisting of coextruding and pressing a film, wherein the film comprises an antistatic and adherent composition layer comprising polyamide, characterized in that the composition further comprises a sufficient quantity of carbon black to be simultaneously antistatic and adherent to at least one adhesive binder for fluoropolymers; an adhesive binder layer; and a fluoropolymer layer. 
     
     
       18. A process for forming the article of manufacture of claim 10 whereby the article of manufacture is formed by at least one method selected from the group consisting of coextruding and pressing a film, wherein the film comprises an inner layer in contact with hydrocarbons, comprising an antistatic and adherent composition layer comprising polyamide, characterized in that the composition further comprises a sufficient quantity of carbon black to be simultaneously antistatic and adherent to at least one adhesive binder for fluoropolymers; a middle layer comprising a fluoropolymer; and an outer layer comprising a polyamide, and wherein each layer is bonded to the adjacent layer by an adhesive binder. 
     
     
       19. The process of claim 7, wherein the polyamide is PA-12 with an inherent viscosity of approximately 1.45 in m-cresol, and wherein the carbon black has a specific surface area of 1250 m 2  /g and a pore volume of 400 ml of dibutyl phthalate per 100 g of carbon black. 
     
     
       20. The process of claim 19, wherein the carbon black comprises from 5.5% to 6.5% by weight of the composition.